Head slider and magnetic recording device therewith

ABSTRACT

A head slider that can furnish excellent head flying stability and a magnetic recording device having excellent head flying stability are provided. For the head slider, the protective layer is composed of two layers, that is, a lower layer and an upper layer thereon; the ionization potential of the lower layer is made to be smaller than that of the upper layer; and the surface free energy of the upper layer is made to be 45 mN/m or less.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional of application Ser. No. 11/047,364, filed Jan. 31,2005.

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2004-251418, filed on Aug. 31,2004, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic recording medium and a headslider.

2. Description of the Related Art

In a magnetic recording device that is generally widely used as anexternal storing unit for computers and other various informationterminals, a head slider equipped with a recording transducer (alsosimply referred to as “head” in the present invention) reads and writesinformation, while flying (or floating) over a magnetic recording medium(also simply referred to as “medium” in the present invention) such as ahard disc.

The distance between the head and a magnetic layer that records (writes)and/or reproduces (reads) magnetic information on the hard disk, iscalled a magnetic spacing. The smaller the magnetic spacing is, the moreimproved the recording density is. Accordingly, the present level of thehead floating gap has become as small as 10 nm or less as a result of astrong need for higher recording density in recent years. In such anultra-small floating gap, only a small amount of contaminants adheredonto a head slider may make the flying stability (or floating stability)of the head greatly out of balance.

Volatile organic materials, debris, etc. brought about from theenvironment are examples of such contaminants. As the head slider moves,volatile organic materials, debris, etc. adhered to the hard disk arescraped together and collected on the head slider, and eventually fillin the head floating gap, resulting in head crashing.

Furthermore, it is known that the lubricant is transferred from thesurface of the medium to the head slider surface side by means ofevaporation from the medium and intermittent contact with the headslider, etc., with the result that a film as thick as the lubricantlayer on the medium is formed inevitably on the outermost head slidersurface facing the medium (also referred to as “ABS” that is anabbreviation of “air bearing surface”).

In a device having a sufficiently wide floating gap, that is, a devicewith a low recording density, such lubricants adhered to the ABS havebeen posing little problem. However, as the floating gap has been madevery small as in the devices at the present day, such a behavior hascome to be on the level that cannot be ignored as a factor for makingthe flying of the head unstable. It is understood that the instabilityof the flying is caused by the lubricant on the ABS contacting with thelubricant of the medium, and forming a liquid bridge.

As a method to solve the above-described problem, it is proposed toinstall a lubricant layer made of a water-repellent resin having anaverage film thickness of 1.5 nm or less on the surface of a head sliderprotective layer that faces the magnetic recording medium, so as todecrease the surface tension of the head slider surface (Japanese PatentApplication No. 16-156468). It is to be noted that carbon-type materialssuch as amorphous carbon are considered to be desirable for the headslider protective layer from the viewpoint of heat resistance, corrosionresistance and abrasion resistance, and carbon-type protective layersdeposited by the sputtering method and the CVD (Chemical VaporDeposition) method are used in general.

One distinguished feature of such a method is that the lubricant appliedonto the head slider is subjected to a UV (ultraviolet) irradiationtreatment so that the lubricant layer is transformed from a liquid-likestate in which it is easily deformed and mobilized into a state in whichit is hard to be deformed and mobilized, and also it is tightly adheredto the head slider surface. Using this head slider, not only is theadhesion of contaminants decreased, but also it is hard for the liquidbridge to be formed with the lubricant applied to the magnetic recordingmedium.

It is thought that the effect of the above-described UV ray irradiationis brought about by the progress of chemical bonding between thelubricant and the head slider protective layer which is caused byactivated points in the lubricant formed by photoelectrons excited inand emitted from the head slider protective layer.

However, amorphous carbons widely used as materials for the presentprotective layer, have a low photoelectron emission efficiency, sincetheir ionization potential is as high as about 5.8 eV. Accordingly, along UV irradiation process is necessary so as to acquire a sufficientforce of adhesion. Such long UV irradiation will accelerate thedecomposition of the lubricant, causing thinning of the film anddeterioration of the adhesion force that is considered to be due to thelowering of the molecular weight, with the result that there occurproblems such as deterioration of the adhesion rate of the lubricant tothe head slider surface, and degradation of the adhesion uniformity thataccompanies the adhesion rate deterioration.

While the above explanation is made on a head slider, similartechnologies can be also applied to the lubricant layer on a magneticrecording medium, and therefore, there are similar problems. Althoughtechnologies such as one in which an adhesion force reinforcingsubstance interposed in between is adhered to the protective layersurface, are disclosed regarding the magnetic recording mediumprotective layer (Japanese Unexamined Patent Application Publication No.03-25723, for example), they are still insufficient.

It is an object of the present invention to solve such problems andprovide a magnetic recording medium and a head slider that can furnishexcellent head flying stability, as well as a magnetic recording devicehaving a head with an excellent head flying stability. It is anotherobject of the present invention to provide a method for manufacturing amagnetic recording medium and a head slider that can furnish excellenthead flying stability in a short time. Other objects and advantages ofthe present invention will be clarified through the followingexplanation.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, provided is a magneticrecording medium formed by layering on a substrate, a magnetic layer, amagnetic recording medium protective layer and a magnetic recordingmedium lubricant layer in this order, wherein: the magnetic recordingmedium protective layer is composed of two layers, that is, a lowerlayer contacting with the magnetic layer and an upper layer on the lowerlayer; the ionization potential of the lower layer is smaller than thatof the upper layer; and the surface free energy of the upper layer is 45mN/m or less.

Similarly, provided is a head slider having a recoding transducer forrecording to and/or reproducing the record from a magnetic recordingmedium, wherein: a head slider lubricant layer is installed on a headslider protective layer; the head slider protective layer is composed oftwo layers, that is, a lower layer and an upper layer on the lowerlayer; the ionization potential of the lower layer is smaller than thatof the upper layer; and the surface free energy of the upper layer is 45mN/m or less.

Regarding each of these aspects, preferable are that the ionizationpotential of the lower layer is 5.5 eV or less; that the film thicknessof the upper layer is not less than 0.5 nm and not more than 1 nm, thatthe total film thickness of the protective layer is not more than 3 nm;that the materials for the upper and lower layers have a hardness of notless than 15 GPa, respectively; that at least one of the lower layer andthe upper layer is formed by deposition by the Filtered Cathodic Arcmethod; that at least one of the lower layer and the upper layercomprises carbon as a main component; that at least one of the lowerlayer and the upper layer comprises an amorphous carbon as a maincomponent; that the upper layer comprises at least one element ofhydrogen and fluorine; that the lower layer comprises at least oneelement of nitrogen and oxygen; that the lubricant layer is subjected toan irradiation treatment of active energy rays; and that the lubricantlayer is water-repellent.

By these aspects of the present invention, magnetic recording media andhead sliders with excellent head flying stability are realized.

According to other aspects of the present invention, provided is amagnetic recording device equipped with the above-described magneticrecording medium, the above-described head slider, or both of them.

By these aspects of the present invention, magnetic recording deviceswith excellent head flying stability are realized.

According to still another aspect of the present invention, provided isa method for manufacturing a magnetic recording medium formed bylayering on a substrate, a magnetic layer, a magnetic recording mediumprotective layer and a magnetic recording medium lubricant layer in thisorder, comprising: composing the magnetic recording medium protectivelayer from two layers, that is, a lower layer contacting with themagnetic layer and an upper layer on the lower layer; and making theionization potential of the lower layer smaller than that of the upperlayer, and the surface free energy of the upper layer 45 mN/m or less.

Also provided is a method for manufacturing a head slider having arecoding transducer for recording to and/or reproducing the record froma magnetic recording medium, comprising: installing a head sliderlubricant layer on a head slider protective layer; composing the headslider protective layer from two layers, that is, a lower layer and anupper layer on the lower layer; and making the ionization potential ofthe lower layer smaller than that of the upper layer, and the surfacefree energy of the upper layer 45 mN/m or less.

Regarding each of the two aspects, preferable are that the ionizationpotential of the lower layer is made to be 5.5 eV or less; that the filmthickness of the upper layer is made to be not less than 0.5 nm and notmore than 1 nm, that the total film thickness of the protective layer ismade to be not more than 3 nm; that the materials for the upper andlower layers have a hardness of not less than 15 GPa, respectively; thatat least one of the lower layer and the upper layer is formed bydeposition by the Filtered Cathodic Arc method; that at least one of thelower layer and the upper layer comprises carbon as a main component;that at least one of the lower layer and the upper layer comprises anamorphous carbon as a main component; that the upper layer comprises atleast one element of hydrogen and fluorine; that the lower layercomprises at least one element of nitrogen and oxygen; that thelubricant layer is subjected to an irradiation treatment of activeenergy rays; and that the lubricant layer is water-repellent.

By these aspects of the present invention, technologies formanufacturing a magnetic recording medium and head slider with excellenthead flying stability in a short time are realized.

All in all, magnetic recording media and head sliders with excellenthead flying stability, magnetic recording devices with excellent headflying stability can be provided. It is also possible to manufacturemagnetic recording media and head sliders with excellent head flyingstability in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the relationship between the adsorption amountof DOP and the surface free energy;

FIG. 2 is a chart showing the result of the observation of the adsorbedwater by the TDS;

FIG. 3 is a schematic view illustrating the structure of an FCA device;

FIG. 4 is a graph showing the relationship between the lubricantadhesion rate and the ionization potential;

FIG. 5 is a graph showing the relationship between the lubricantadhesion rate and the duration of irradiation with active energy rays;

FIG. 6 is a schematic plan view illustrating the internal structure of ahard disc device; and

FIG. 7 is a schematic side cross-sectional view illustrating therelationship between a head and a magnetic recording medium.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments according to the present invention will be described withreference to the following figures, tables, equations, examples, etc. Itis to be understood that these figures, tables, equations, examples,etc., plus the explanation below are for the purpose of illustrating thepresent invention, and do not limit the scope of the present invention.It goes without saying that other embodiments should also be included inthe category of the present invention as far as they conform to the gistof the present invention. In the figures, the same sign indicates thesame element.

In the following, the present invention will be explained mainly on harddisk devices. However, any head slider may be a “head slider” accordingto the present invention, including one operating with theloading-unloading mechanism, one operating with the contact-start-stopmechanism, one with which information is recorded and reproduced by thecomplete floating method, one with which information is recorded andreproduced by the gas-liquid mixing method and one with whichinformation is recorded and reproduced by the contact method, besidesthose for hard disc devices Also, any recording medium may be a“magnetic recording medium” according to the present invention,including a longitudinal recording medium, an SFM (SyntheticFerrimagnetic Medium or Antiferromagnetically Coupled Medium), avertical recording medium, and a patterned medium used for hard diskdevices. Furthermore, any magnetic recording device using such a headslider and/or magnetic recording medium is included in the “magneticrecording device” according to the present invention.

It is to be noted that a protective layer for a magnetic recordingmedium is called a magnetic recording medium protective layer or mediumprotective layer, and a protective layer for a head slider is called ahead slider protective layer or head protective layer, in the presentinvention. When both cases are referred to, the simple term “protectivelayer” is used.

Also, a lubricant layer for a magnetic recording medium is called amagnetic recording medium lubricant layer or medium lubricant layer, anda lubricant layer for a head slider is called a head slider lubricantlayer or head lubricant layer. When both cases are referred to, thesimple term “lubricant layer” is used.

In addition, when the terms upper and lower layers are used, a layerthat is closer to the outermost layer is called an upper layer, and alayer that is less closer to the outermost layer is called a lowerlayer, for both of the medium and head slider.

FIG. 6 is a schematic plan view depicting the internal structure of ahard disk device, and FIG. 7 is a schematic side cross-sectional view (across-sectional view cut in a direction perpendicular to the magneticlayer surface of the magnetic recording medium) depicting therelationship between a head and a magnetic recording medium.

This hard disk device comprises, as main components, a magneticrecording medium 1, a head slider 2 that has a head, a rotation controlmechanism (e.g. spindle motor) 3 for the magnetic recording medium 1, apositioning mechanism 4 for the head, and a processing circuit (e.g.read/write amplifier) 5 for recording/reproducing signals, as shown inFIG. 6.

As FIG. 7 shows, the head slider 2 is connected with the positioningmechanism 4 for the head by a suspension 6 and gimbals 7 for flexiblysupporting the head slider 2, and a head 8 is installed at the tip ofthe head slider 2. On the head slider surface, a head protective layer 9and a head lubricant layer 10 are formed.

A magnetic recording medium 11 is comprised of a substrate 12, Crunderlayer 13, magnetic layer 14, medium protective layer 15, mediumlubricant layer 16, etc. from the bottom to top in FIG. 7. Other layersincluding a seed layer may also be installed, but they are not shown inthis figure. In the case of a hard disk device, the thickness of themedium lubricant layer is about 1-2 nm, the thickness of the mediumprotective layer is about 3-5 nm, the thickness of the magnetic layer isabout 20 nm, and the thickness of the Cr underlayer is about 10 nm, ingeneral.

In such configurations, the above-described problems can be solved by amagnetic recording medium formed by layering on a substrate, a magneticlayer, a medium protective layer and a medium lubricant layer in thisorder, wherein: the medium protective layer is composed of two layers,that is, a lower layer contacting with the magnetic layer and an upperlayer on the lower layer; the ionization potential of the lower layer issmaller than that of the upper layer; and the surface free energy of theupper layer is 45 mN/m or less, or by a head slider having a recordingtransducer for recording to and/or reproducing a record from a magneticrecording medium, wherein: a head lubricant layer is installed on a headprotective layer; the head protective layer is composed of two layers,that is, a lower layer and an upper layer on the lower layer; theionization potential of the lower layer is smaller than that of theupper layer; and the surface free energy of the upper layer is 45 mN/mor less.

In general, by lowering its ionization potential, the photoelectronemission efficiency of a protective layer is increased, with the resultthat the adhesion rate of a lubricant and the protective layer can beimproved, while greatly cutting down the irradiation duration of activeenergy rays such as UV rays. In order to decrease the ionizationpotential, it is efficient and easy to dope oxygen or nitrogen into theprotective layer.

However, if the surface free energy increases when the ionizationpotential is made smaller, the problem of contaminants tending to beeasily adsorbed occurs. Such increase of surface free energy becomesconspicuous, when oxygen or nitrogen is doped into the protective layeras a means to decrease the ionization potential.

On the other hand, when the surface free energy of the protective layeris made smaller, the problem of the ionization potential tending to beincreased, would come about. For example, while it is effective to dopeat least one element of fluorine and hydrogen into the protective layerso as to decrease the surface free energy of the protective layer, theionization potential is generally increased in such a protective layer,with the result that the photoelectron emission efficiency is decreased.

Such a problem can be avoided by making the ionization potential of thelower layer smaller than that of the upper layer, and making the surfacefree energy of the upper layer 45 mN/m or less, at the same time.

In this case, a sufficient amount of photoelectrons are generated byactive energy rays such as UV rays that pass through the upper layer andreach the lower layer, with the result that the adhesion rate betweenthe lubricant and the protective layer is increased, and the adsorptionof the contaminants can be prevented by making the surface free energyof the upper layer 45 mN/m or less.

Therefore, it is possible to obtain a magnetic recording medium and ahead slider that can furnish excellent head flying stability by applyingthe present invention. It is also possible to manufacture such amagnetic recording medium and a head slider as those described abovethat can furnish excellent head flying stability in a short time, byraising the photoelectron emission efficiency.

To make the surface free energy of the upper layer 45 mN/m or less, itis preferable that the upper layer comprises at least one element ofhydrogen and fluorine. There is no particular limitation to the contentsof fluorine and hydrogen. It is preferable to have elements such asmetals, nitrogen, oxygen as little as possible in the upper layer,especially in the area close to the surface of the upper layer, sincethey tend to adsorb contaminants.

In addition, it is preferable that the lower layer comprises at leastone element of nitrogen and oxygen, so as to make the ionizationpotential of the lower layer smaller than that of the upper layer. Inthis case, fluorine and hydrogen may also be present as long as it isnot against the gist of the present invention. Although there is noparticular limitation to the contents of nitrogen and oxygen, it ispreferable that the ionization potential of the lower layer is 5.5 eV orless. When it exceeds 5.5 eV, there are cases in which the amount ofgenerated photoelectrons is insufficient.

It is preferable that the film thickness of the upper layer is not lessthan 0.5 nm and not more than 1 nm. If it is less than this range, therewould be a possibility that formation of a uniform film as the upperlayer becomes difficult, with the result that the lower layer is partlyexposed and tends to adsorb contaminants. When it exceeds this range,the probability of photoelectrons being deactivated before activatedpoints are formed in the lubricant becomes larger, since the filmthickness of the upper layer becomes comparable to the average free pathof the photoelectrons generated in the lower layer. It is to be notedthat it is preferable that the total film thickness of the protectivelayer is not more than 3 nm, so as to decrease the magnetic spacing.

In addition, it is preferable that the materials for the upper and lowerlayers have a hardness of not less than 15 GPa, respectively. Valuesless than the value tend to cause trouble to the primary object of theprotective layer, that is, to prevent the head and the magnetic layer ofthe medium from being mechanically damaged.

The upper and lower layers are not necessarily clearly discernable fromeach other, physically or compositionally. It is sufficient if theabove-described relationship holds when an upper layer part and a lowerlayer part of a protective layer are compared. A concentration gradientmay exist. To be specific, a protective layer according to the presentinvention may be obtained, by using one the same amorphous carbon as themain components for both the upper and lower layers, doping at least oneelement of nitrogen and oxygen when the lower layer is formed, followedby preparation of the upper layer in which supply of these elements isceased and then at least one element of fluorine and hydrogen is doped.It is not always necessary to start supplying the fluorine and/orhydrogen after the nitrogen and/or oxygen is completely removed from thesystem, or a state in which they are present at the same time, may beallowed.

Such a combination of upper and lower layers can be easily selected byactually forming them as single layers, and measuring the ionizationpotential and the surface free energy.

To form a protective layer comprising upper and lower layers accordingto the present invention, there is a method, to be specific, in whichthe Filtered Cathodic Arc method (the FCA method) is employed, forexample, and when the lower layer is formed, doping is performed by ionassisting, using an ion gun or the like so as to have nitrogen or oxygenalso present in the lower layer, and when the upper layer is formed,doping is performed by ion assisting, using an ion gun or the like so asto have fluorine or hydrogen also present in the upper layer. A nitrogengas can be used as a raw material for doping with nitrogen, an oxygengas can be used as a raw material for doping with oxygen, a hydrogen gascan be used as a raw material for doping with hydrogen, andtetrafluoromethane can be used as a raw material for doping withfluorine.

Besides the FCA method, sputtering and the CVD method may be applied toform a protective layer comprising an upper layer and lower layeraccording to the present invention.

Any material may be used as a component for the composition of the upperlayer or lower layer. It is preferable to use a carbon, particularly anamorphous carbon as a main component. As other components for thecomposition, TiO₂, Cr₂O₃, CrN, WC, TiC, ZrC, Si, SiC, Al₂O₃, BN, SiN,etc. are examples. As materials for the head slider, Al₂O₃—TiC, silicon,sapphire, etc. are examples.

Any method can be applied besides the above-described FCA method forobtaining a layer composed of a carbon such as an amorphous carbon. Itis to be noted that “comprising as a main component” according to thepresent invention means that the component exceeds 50 atom %. For thecomposition of the upper layer, it is more preferable that not less than90 atom % is a carbon.

It is to be noted that the film hardness can be raised by compacting thecomposition, for example, by having more sp³ carbon structure. From thisviewpoint, it is preferable for the upper layer to have a density notless than 2.5 g/cm³. An amorphous carbon is particularly preferable.

An amorphous carbon can be prepared by the FCA method as follows. FIG. 3is a schematic view of a FCA deposition system to perform the FCAmethod. In reference to FIG. 3, a carbon source such as graphite is usedas a cathode 31. Arc discharging is caused between the cathode 31 and ananode 32 to generate carbon ions, electrons, carbon neural atoms andcarbon macroparticles, from which the carbon neutral atoms and carbonmacroparticles are removed by magnetic filters (filter coils 33 and 34)so that only the carbon ions and electrons are sent to a substrate 35.Thus, a DLC (diamond-like carbon) layer 36 is formed on the substrate.An ion gun 37 can be used for doping with other elements.

With the FCA method, it is easy, based on the deposition principle, toincrease the amount of sp³ bonding that is generally called diamondbonding, to 50% or more of the total bonding. Accordingly, it ispossible to realize a hardness and density similar to those of diamondin an amorphous form.

It is important to subject the lubricant layer formed on the protectivelayer according to the present invention to an irradiation treatmentwith active energy rays. The chemical bonding between the lubricant andthe protective layer progresses by formation of activated points in thelubricant caused by photoelectrons excited in and emitted from theprotective layer by means of active energy ray irradiation.

Any known active energy rays may be used for this purpose as long as itis not against the gist of the present invention. UV rays, excimer rays,X-rays, electron beams, focused ion beams, etc. can be used. Xenonexcimer rays and electron beams are particularly preferable. Irradiationtime can be determined appropriately. When the irradiation treatmentwith active energy rays is performed, it is possible to change the stateof the lubricant layer from a liquid-like state in which the layer iseasily deformed and mobile to a state in which the layer is hard to bedeformed and hard to move, and also to firmly adhere the layer to thesurface of the protective layer. It is possible to confirm that thelayer is firmly adhered to the surface of the protective layer, byevaluating the film thickness of the lubricant layer after the washingof the lubricant on the surface of the protective layer with a solvent.

Any material may be used for the lubricant layer according to thepresent invention, as long as it does not contradict the gist of thepresent invention. Those containing a fluororesin are preferable. As afluororesin for the purpose, fluorinated hydrocarbons that may bebranched, fluorinated polyethers that may be branched, or mixturesthereof can be enumerated. Perfluorinated hydrocarbons that may bebranched, perfluoropolyethers that may be branched, or mixtures thereofare more preferable. The more the fluorine content in a molecule is, theless the coagulation properties are, and accordingly, it is possible toform a uniform layer with a small surface tension. Regarding thefluorine content, the ratio of the mole number of fluorine to the totalmole number of fluorine and hydrogen in a molecule is preferably notless than 80%, more preferably not less than 90%, and still morepreferably not less than 95%. It is to be noted that the weight-averagemolecular weight of the resin is preferably in the range of from 2,000to 20,000.

The lubricant layer preferably contains not less than 95 wt. % of afluororesin. More preferably, it substantially consists of a fluororesinexcept minor components such as a catalyst.

By the above-described present invention, it is possible to realize amedium and head slider wherein not only the amount of adheredcontaminants is reduced but also liquid-bridging between the medium andhead slider is hard to occur. Accordingly, a magnetic recording mediumand head slider that can furnish excellent head flying stability, arerealized. It is also possible to manufacture such a medium and headslider in a short time.

Furthermore, using a magnetic recording device employing at least one ofsuch a medium and head slider, head crashing is hard to occur, and thereliability is improved. Accordingly, it is possible to realize amagnetic recording device having an excellent head flying stability.

EXAMPLES

Next, examples according to the present invention will be described indetail. It is to be noted that the physical properties were determinedas follows.

(Fluorine Content and Nitrogen Content)

The fluorine content and nitrogen content were quantitatively determinedusing the X-ray photoelectron spectroscopy (XPS).

(Film Hardness)

The nanoindentation method was used for determining the film hardness.The nanoindentation method is a method in which a diamond indenter ispressed into a material by means of a tiny amount of load on the orderof a μN so that mechanical properties are evaluated by measuring a tinydeformation under the unloading. Since the pressed-in amount can belimited to several nm, it is suitable for evaluating properties of thinfilm samples.

(Surface Free Energy of a Film)

Surface free energy was determined by measuring the contact angles ofpure water and diiodomethane on a film object, followed by thecalculation using the following equations.

When γ_(S) is a surface free energy of a solid sample, γ_(L) is asurface free energy of a liquid sample, θ_(SL) is a contact angle of asolid sample/liquid sample, and γ_(SL) is an interfacial free energy ofa solid sample/liquid sample, then the Young's equation as shown inequation (1) holds.γ_(S)=γ_(L)·cos θ_(SL)+γ_(SL)  (1)

On the other hand, the adhesion work W_(SL), or an energy for thestabilization by adherence of a liquid to the surface of a solid,follows the Dupre equation (2).γ_(S)+γ_(L) =W _(SL)+γ_(SL)  (2)

The Young-Dupre equation (3) is derived from the two equations, andaccordingly, the adhesion work can be obtained from the surface freeenergy and a contact angle of a liquid.W _(SL)=γ_(L)(1+cos θ_(SL))  (3)

Equation (4) holds when the geometric mean rule for each surface freeenergy component is applied to the adhesion work.W _(SL)=2√{square root over ( )}(γ_(S) ^(d)·γ_(L) ^(d))+2√{square rootover ( )}(γ_(S) ^(h)·γ_(L) ^(h))  (4)

Here, d and h are a dispersion component and a hydrogen bondingcomponent, respectively.

The following relationship holds regarding the adhesion work when twodifferent liquids (i,j) are used.

$\begin{matrix}{\begin{pmatrix}W_{SL}^{i} \\W_{SL}^{j}\end{pmatrix} = {2\begin{pmatrix}\sqrt{\gamma_{L}^{d,i}} & \sqrt{\gamma_{L}^{h,i}} \\\sqrt{\gamma_{L}^{d,j}} & \sqrt{\gamma_{L}^{h,j}}\end{pmatrix}\begin{pmatrix}\sqrt{\gamma_{S}^{d}} \\\sqrt{\gamma_{S}^{h}}\end{pmatrix}}} & (5)\end{matrix}$

Accordingly, if the adhesion work is determined through actuallymeasuring contact angles for two different liquids, the surface freeenergy of a solid can be obtained for each component by the followingrelationship. This relationship is called the Fowkes equation.Furthermore, the surface free energy: γ=γ^(d)+γ^(h) can be obtained fromthe relationship.

$\begin{matrix}{\begin{pmatrix}\sqrt{\gamma_{S}^{d}} \\\sqrt{\gamma_{S}^{h}}\end{pmatrix} = {\frac{1}{2}\begin{pmatrix}\sqrt{\gamma_{L}^{d,i}} & \sqrt{\gamma_{L}^{h,i}} \\\sqrt{\gamma_{L}^{d,j}} & \sqrt{\gamma_{L}^{h,j}}\end{pmatrix}^{- 1}\begin{pmatrix}W_{SL}^{i} \\W_{SL}^{j}\end{pmatrix}}} & (6)\end{matrix}$

(Ionization Potential)

Ionization potential was determined by UPS (Ultraviolet PhotoelectronSpectroscopy).

(Amount of Adsorbed Water)

Amount of adsorbed water was determined as a degasification intensity ofwater by the TDS (Thermal Desorption Method). This is a method in whichwater that is released while a sample is being warmed up, is evaluatedby the intensity data of a mass spectrometer.

(Amount of Adsorbed DOP)

The amount of DOP adsorbed during exposure testing was determined byGC/MS (Gas Chromatograph/Mass Spectrometer).

(Rate of Adhered Lubricant)

Samples were rinsed with 2,3-dihydrodecafluoropentane. The rate ofadhered lubricant was determined as the percentage rate of the filmthickness of a lubricant layer after the rinsing to that before therinsing. The film thickness was measured by XPS.

Example 1

An amorphous carbon protective layer having a film thickness of 30 nmwas deposited on a head slider substrate made of Al₂O₃—TiC, as a headprotective layer. Using an FCA apparatus as shown in FIG. 3 and agraphite target as a raw material, the amorphous carbon protective layerwas deposited at a deposition speed of 0.1 nm/second, under theconditions: 60 A for the arc current; 30 V for the arc voltage; and 10 Afor the current of the cathode coil. During the deposition, a nitrogengas was supplied to the deposition chamber to perform doping withnitrogen during the deposition in the atmosphere. The film properties ofa single film formed by these conditions are indicated in TABLE 1.

TABLE 1 CONTENT OF FILM NITROGEN HARDNESS IONIZATION SURFACE FREE (atom%) (GPa) POTENTIAL (eV) ENERGY (mN/m) 10 19 5.5 63

Example 2

An amorphous carbon protective layer having a film thickness of 30 nmwas deposited on a head slider substrate made of Al₂O₃—TiC, as a headprotective layer. The head protective layer was prepared in the same wayas for EXAMPLE 1, except that tetrafluoromethane (CF₄) was suppliedinstead of a nitrogen gas. The film properties of a single film formedby these conditions are indicated in TABLE 2.

TABLE 2 CONTENT OF FILM FLUORINE HARDNESS IONIZATION SURFACE FREE (atom%) (GPa) POTENTIAL (eV) ENERGY (mN/m) 13 25 6.1 45

Example 3

An amorphous carbon protective layer having a film thickness of 30 nmwas deposited on a head slider substrate made of Al₂O₃—TiC, as a headprotective layer. The head protective layer was prepared in the same wayas for EXAMPLE 1, except that no atmospheric gas was supplied. The filmproperties of a single film formed by these conditions are indicated inTABLE 3.

TABLE 3 FILM HARDNESS IONIZATION SURFACE FREE (GPa) POTENTIAL (eV)ENERGY (mN/m) 30 5.8 53

Example 4

An amorphous carbon protective layer was deposited on a head slidersubstrate made of Al₂O₃—TiC, as a head protective layer. Three type ofsamples were prepared: sample A on which a 3 nm thick head protectivelayer was formed in the same way as for EXAMPLE 1; sample B on which a 3nm thick head protective layer was formed in the same way as for EXAMPLE2; and sample C on which a 3 nm thick head protective layer was formedin the same way as for EXAMPLE 3.

As a result of observation by the TDS of the amounts of adsorbed waterof these samples that is to cause corrosion of the magnetic layer, itwas found as shown in FIG. 2 that the smaller the surface free energy,the less the amount of adsorbed water.

Next, using DOP (dioctyl phosphate) that is contained in a plasticizerfor plastics as an indicator material of contaminants on the medium andhead slider, the amount of adhered DOP was investigated.

To be specific, all samples and DOP were placed in the same deccicator,and the samples were exposed to the DOP vapor for 24 hours. Then, theamount of adsobed DOP on each sample was determined using GC/MS. Theresult is shown in FIG. 1. The amount of adsobed DOP indicated the sametendency as the amount of adsorbed water, that is, the smaller thesurface free energy, the less the amount of adhered DOP water.

Furthermore, in order to investigate the rate of adhesion of a lubricanton each sample, perfluoropolyether (both molecular terminals beingtrifluoromethy groups and the average molecular weight being 9,500) wasapplied to form a film having an average film thickness of 1 nm, axenone excimer light (wave length being 172 nm) was irradiated in anitrogen atmosphere for 30 seconds, and then, the rates of adheredlubricant were determined from the change in the film thickness of thelubricant before and after the rinsing of the head lubricant layer with2,3-dihydrodecafluoropentane. As shown in FIG. 4, the adhesion of thelubricant was improved. This is because the rate of efficiency in thegeneration of photoelectrons is increased as the ionization potential ismade smaller.

Example 5

An amorphous carbon protective layer having a film thickness of 3 nm wasdeposited on a head slider made of Al₂O₃—TiC, as a head protectivelayer.

The amorphous carbon protective layer was formed by forming a 2 nm thicklower layer in the same way as for EXAMPLE 1, and forming a 1 nm thickupper layer in the same way as for EXAMPLE 2, thus making the totalthickness 3 nm.

After that, perfluoropolyether (both molecular terminals beingtrifluoromethy groups and the average molecular weight being 9,500) wasapplied onto the surface of the head slider to form a film having anaverage film thickness of 1 nm, and a xenone excimer light (wave lengthbeing 172 nm) was irradiated in a nitrogen atmosphere. FIG. 5 indicatesthe change in the rate of adhered lubricant according to the irradiationtime. The adhesion rate was 55% at an irradiation time of 15 seconds,and it reached 70% or higher in 60 seconds.

Example 6

An amorphous carbon protective layer having a film thickness of 3 nm wasdeposited on a head slider made of Al₂O₃—TiC, as a head protectivelayer, as in EXAMPLE 5. The amorphous carbon protective layer having athickness of 3 nm was formed in the same way as for EXAMPLE 3.

After that, perfluoropolyether (both molecular terminals beingtrifluoromethy groups and the average molecular weight being 9,500) wasapplied onto the surface of the head slider to form a film having anaverage film thickness of 1 nm, and a xenone excimer light (wave lengthbeing 172 nm) was irradiated in a nitrogen atmosphere. FIG. 5 indicatesthe change in the rate of adhered lubricant according to the irradiationtime. Ninety seconds was needed for the irradiation to reach an adhesionrate of 55%, and no increase of the adhesion rate was observed eventhough the irradiation was continued after that.

1. A head slider having a recording transducer for recording to and/orreproducing a record from a magnetic recording medium, wherein: a headslider lubricant layer is installed on a head slider protective layer;said head slider protective layer consists of two layers, that is, alower layer and an upper layer on the lower layer; an ionizationpotential of said lower layer is smaller than that of said upper layer;and surface free energy of said upper layer is 45 mN/m or less.
 2. Ahead slider according to claim 1, wherein the ionization potential ofsaid lower layer is 5.5 eV or less.
 3. A head slider according to claim1, wherein a film thickness of said upper layer is not less than 0.5 nmand not more than 1 nm.
 4. A head slider according to claim 1, wherein atotal film thickness of said head slider protective layer is not morethan 3 nm.
 5. A head slider according to claim 1, wherein materials forsaid upper and lower layers have a hardness of not less than 15 GPa,respectively.
 6. A head slider according to claim 1, wherein at leastone of said lower layer and said upper layer is formed by deposition bya Filtered Cathodic Arc method.
 7. A head slider according to claim 1,wherein at least one of said lower layer and said upper layer comprisescarbon as a main component.
 8. A head slider according to claim 1,wherein at least one of said lower layer and said upper layer comprisesan amorphous carbon as a main component.
 9. A head slider according toclaim 1, wherein said upper layer comprises at least one element ofhydrogen and fluorine.
 10. A head slider according to claim 1, whereinsaid lower layer comprises at least one element of nitrogen and oxygen.11. A magnetic recording device equipped with a head slider according toone of claims 1 to 10.